Marie-Louise Rossi is leaving the Internatinal Underwriting Association (IUA) to pursue a career in politics.
Rossi has spent more than six years with the organisation. Before its formation she headed up the London International Insurance and Reinsurance Market Association.
She spearheaded the organisation when it merged with the Institute of London Underwriters to form the IUA in 1999.
Rossi will stand down from the post to fight for a seat for the Liberal Democrats in the next general election. She has not ruled out returning to the market at a later date, however.
The IUA said it would announce Rossi's successor shortly.
